learn to spot where they are going to shoot the fireworks. you should orient your horizontal axis of tripod to that point, and lock it. then tilt upwards around 45 degree and above (depending on your elevation - I am assuming unobstracted ground level around the marina bay perimeter).
Lock the vertical there, or make it tight so you can still get it.
Shoot with both eye open. Appreciate the music cos sometimes the firework is timed together with the music so you know roughly when it will spark in the sky.
If you can roughly pre-focus then good, if you cannot then use auto focus but you have to be extremely quick.
Use bulb mode if you have the option, but if not 3 - 4 seconds is good enough.
ISO set to around 400. Shoot raw prefereably so you can tweak white balance better. If not then use expodisc if you have auto-white balance function aiming at the ambient lights of buildings at the horizon assuming you will include them in the background.
Normally the first 10 seconds will give you the best shot. After than it will be lousy because the smoke lingers if there is no strong wind to blow it away and cause over exposure (bright clouds).
It is hit and miss kind. If you dont get any good one, well there will always be another firework.
and by the way, good spots will run out 2 hours before the firework starts. it is common to see people reserving good spot from 5 pm onwards. Seriously!